Evangeline Lilly says she used to dream of being a wood elf. And now she is one.

The actress, best known for “Lost,” spent a considerable amount of her Canadian childhood absorbed in J.R.R. Tolkien’s tales of Middle-earth. So it’s a tad ironic that her character in “The Hobbit: The Desolation of Smaug” – opening Friday – appears nowhere in the Tolkien canon.

“She’s a complete fabrication,” Lilly said of Tauriel, the deadly archer/knife-fighter/head of the Mirkwood Elven Guard – and the virtual centerpiece of director Peter Jackson’s latest. Of course, the only character with any real arc in what Lilly called Tolkien’s “little romp” is its title hobbit, Bilbo Baggins. “But as a Tolkien fan,” she said, “I trusted that if anyone could depart from the book and expand it, it was Peter Jackson.”

The Oscar-winning Jackson has been bringing Tolkien’s elves, dwarves, trolls, goblins hobbits – and in “Smaug,” a fire-breathing dragon – to the screen since 2001’s “The Lord of the Rings: The Fellowship of the Ring.” The movie kick-started a trilogy based on three novels and led to “The Hobbit,” three equally ambitious films based on one small book published in 1937. With the release next year of “The Hobbit: There and Back Again,” the whole thing comes to a close.

Maybe.

“You never say you’re finished with these films,” said Ian McKellen, currently on Broadway in the alternating “Waiting for Godot”/“No Man’s Land” production, and whose wizard Gandalf is the one character to appear in every one of Jackson’s Tolkien movies.

“Suddenly, there’s more filming to be done,” McKellen said. “And even when you’re done you have to go back and do (voice-overs). I ended up doing my last bit of that only about a month ago. And who knows? There’s the other one coming out this time next year, and there’s also ‘The Silmarillion’ – maybe Peter will decide to do that, too.”

“The Silmarillion,” published posthumously by Tolkien’s son, is a collection of “Ring” ephemera, mythopoetic history about Middle-earth, and more proof of the resilience of Tolkein’s literary fantasies. Written in the years leading up to and following World War II, they have been interpreted in many ways, most of which Tolkien dismissed.

“It’s all fantastical and heightened,” actor Martin Freeman, who plays Bilbo, said of Tolkien’s work. “But there’s got to be something at the root of it all to maintain its enormous appeal. You know, the way they say ‘Star Wars’ is a Western; “The Godfather” was about the ’50s, but it’s really about the ’70s. Substitute trolls for Nazis, or whatever. Things that push our buttons. A lot of it is about loyalty and family and honor and things that are fairly universal, things that are as real today as any time.”

Some audiences will be coming to see how Jackson has monkeyed with the original. Some will be coming for the story and its sense of mission; some will be coming to see how Jackson has furthered the mission of advancing cinema. Like the previous “Hobbit,” the second chapter was shot at 44 frames per second (as opposed to the traditional 24 fps) and is in 3-D. But unlike the first, in which the images possessed a distracting clarity (and were compared to TV soap operas), the new one seems more traditionally cinematic.

“It makes sense that it would look better,” said Freeman. “The technical people at Weta (Jackson’s production company in New Zealand) make progress now on a monthly basis, how they attack things, and render stuff. I would expect it would be better.”

At the same time, the process of acting in a movie so dependent on computer graphics poses a challenge for actors, even if McKellen says there’s less techno in “Smaug” than one might assume.

“If you see Gandalf on top of a mountain, I have been on top of a mountain,” he said. “If you see me crawling through undergrowth, I’ve crawled through undergrowth – although sometimes it’s on a set rather than outside.

“What is difficult is the height disparity,” he said. “Gandalf is taller and that makes it tricky.” It means, for instance, not making eye contact with a fellow actor, because by the time it gets on screen he may be three feet below your eye line. Sometimes, McKellen said, the proper effect is achieved simply by having a taller character stand closer to the camera. Computer graphics do the rest.

“It’s a constant worry and nuisance, really,” McKellen said, “but a great relief when you get to do a scene with a normal-sized man.”

Lilly said she was relieved to see herself on screen doing what she remembered doing.

“I was hoping they didn’t use a stunt double because I know what I did and I think I did it well,” she said. “Some things I knew had to be CGI, because you know ‘I didn’t do that.’ But I honestly couldn’t find the gaps.”

The greatest thing, Lilly said, went far beyond the technical questions.

“If I were a little girl, I would think it would be so cool to be Tauriel,” the actress said. “And that’s me.”